A timeline of inventions

An overview of the inventions which have changed the course of history [1900-1944]

Many inventions have had a Darwinian-like evolution, with rival companies vying to come up with ever-better products, to the benefit of the consumer. But not the vacuum cleaner. For the best part of a century the basic design remained a dinosaur in the technological Lost World.

The first vacuum cleaner was a fairly silly idea cooked up in response to a really silly one. In 1901 a London-based engineer named Hubert Booth saw a new American device for extracting dust from the upholstery of railway carriages. It used compressed air to blast the dust out, which was all very well, except the dust settled straight back on the furniture again.

Booth suggested that perhaps suction might be better, an idea the inventor dismissed as impractical. Booth later decided to put his idea to the test. He put a handkerchief on the floor of his office and sucked hard. The handkerchief was covered with dust. By February 1902, teams of men from Booth's British Vacuum Cleaner Company were turning up at homes with a five-horsepower engine and a huge hose fitted with a filter for cleaning carpets.

Two years later, he introduced an electric-powered machine weighing around 40 kg. Booth's design, with the filter in front of the vacuum section, was not the true ancestor of the conventional vacuum cleaner. That accolade (if such it can be called) goes to James Spangler, an American asthmatic janitor who wanted a way of cleaning that didn't stir up dust and bring on an attack. He came up with a machine with an electric fan that dumped the dust into a pillowcase. In 1908 Spangler sold the rights to a leather and saddle maker looking to diversify. The company's name was Hoover.

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Put on the market at $70 (around £800 in today's money), the Hoover upright machine turned vacuum cleaners into a mass-market product. A few tweaks were added to the design: Electrolux introduced the cylinder model with a hose in 1913, followed 23 years later by a Hoover with beater-brushes. But that was pretty much it until 1978, when I found I'd run out of vacuum bags at home.

Fishing the old one out of the bin, I cut it open with the intention of emptying it, only to find it wasn't very full. After I'd scraped it out, and re-fitted it, the vacuum cleaner still had a feeble suction. I was stunned to discover that the walls of the bag were clogged with dust. The airflow was being choked by the bag walls, causing a dramatic loss of suction.

I became determined to come up with a vacuum cleaner with a performance that did not stand or fall by the properties of a paper bag. Inspired by a paint-spraying device I had seen at our Ballbarrow factory, I focused on using centrifugal force to spin dust out of the air. It sounds simple but it took me 14 years and more than 5,000 prototypes to arrive at the final design: a dual cyclone system that accelerates the dust-laden air to high speed, flinging the dirt out of the air-stream. In February 1993, the first Dyson DC01 machines rolled off the production line. Within two years it was the most popular machine in the UK and today Dyson vacuum cleaners are the most popular in western Europe.

Air conditioning [1902, Willis Carrier]

In 1902, a Brooklyn, NY, printer frustrated by the effects that changes of temperature and humidity had on his paper, contracted Willis Haviland Carrier, a local engineer. Carrier's solution was to invent the world's first air-conditioning machinery. It pumped liquid ammonia through a set of evaporation coils. Warm air in the room heated the ammonia which evaporated, absorbing heat and cooling the air until it reached its dew point. The droplets that formed on the coils drained away and a fan returned the cooler, drier air to the printing plant.

Electrocardiogram [1903, Willem Einthoven]

It had been known since the 17th century that muscular tissue would conduct electricity, and by the late 19th century, physiologists had investigated the possibility that the human body and heart, too, had electrical potential. Then, in 1895, a brilliant young Dutch physiologist, Willem Einthoven, used a crude electrical sensing apparatus to establish that the beating heart produced four distinct signals, each one corresponding to a different ventricle. He called these distinct signals the "pqrs" factors. However, Einthoven needed an exact way of measuring the minute amounts of current.

In 1897 a French electrical engineer, Clement Ader, invented the "string galvanometer", containing a tensioned string of quartz. In 1903, Einthoven modified Ader's machine, adding electrodes attached to the patient's limbs and thorax. In use, the string was seen to vibrate in time with the patient's heart. The vibrations were recorded photographically.

With his "electrocardiogram" Einthoven was able to look at each of the pqrs signals and diagnose the health of the heart. For his pioneering work, Einthoven was awarded the Nobel prize in 1924.

Radar [1904, Christian Hülsmeyer by James Dyson]

During the war, my mother worked for Bomber Command, shunting those little flags representing planes around the map of Europe. She could plot things hundreds of miles away thanks to radio detection and ranging, now known as radar.

After discovering radio waves in 1888, the German scientist Heinrich Hertz proved they could be bounced off things. In 1904, the German engineer Christian Hülsmeyer turned this into a patent for a collision warning system for shipping, the first radar system.

Then in 1935, the Scottish physicist Robert Watson-Watt of the National Physical Laboratory near Slough was asked by the Air Ministry to investigate the possibility of using a beam of radio waves as a death-ray weapon. Watson-Watt found that radio transmitters lacked the power to kill, but that they could trigger echoes from aircraft almost 200 miles away. He was helped by the invention in 1940 of the cavity magnetron, by John Randall and Henry Boot at Birmingham University. This gave a compact, powerful source of short-wave radio waves and thus a means of detecting targets from aircraft at great distances.

Wartime radar experts found their magnetrons could be used as water heaters for their tea. Today magnetrons are the source of heat in microwave ovens.

Colour photography [1904, Auguste and Louis Lumière]

The first photographs, seen in 1839, were greeted with wonder and disappointment. How could a process that recorded nature with such faithful detail fail to record its colours? The search for a method of producing colour pictures became photography's Holy Grail.

In 1904, two Frenchmen, Auguste and Louis Lumière, gave the first public presentation of a colour process they called "autochrome". The brothers had been experimenting with colour for many years and had published an article on the subject in 1895, the year that they invented the cinematographe. Autochrome plates incorporated a filter screen made from transparent grains of potato starch, dyed red, green and blue, the three colours that in 1861, James Clerk Maxwell, a young Scots physicist, had shown could be used to make all colours, a process known as "additive" colour synthesis.

There were about four million microscopic potato starch grains on every square inch of autochrome plate, each of which acted as a tiny coloured filter. The grains combined after processing to produce a full-coloured image. Autochrome plates went into production in 1907 and their success soon prompted the appearance of many similar processes.

At the same time, a number of "subtractive" methods for making colour photographs were under development. These all required negatives to be made through red, green and blue filters. These "colour separation" negatives were then used to make cyan (blue), magenta (red) and yellow prints, which were superimposed to produce a coloured image. Modern colour photography is based on the same concept, but instead of separate negatives, colour film has several layers of emulsion, each of which is sensitive to one of the primary colours.

Kodachrome, the first modern colour film, was invented in America by Leopold Mannes and Leopold Godowsky, nicknamed "Man and God". These classically-trained professional musicians carried out photographic experiments in their spare time, often in hotel rooms when they were on tour. Their musical background was useful when they whistled passages of music to gauge development times in the darkroom.

When Kodak heard about the two Leopolds' work, they were persuaded to give up their musical careers to work full time in the Kodak research laboratories. With the support of Kodak's technical and financial resources, they made rapid progress. Kodachrome cine film first went on sale in 1935, followed by 35mm film for still photography the following year. In 1936, Agfa introduced a similar multi-layer film, called Agfacolor.

With the perfection of dye-based multi-layer films such as Kodachrome and Agfacolor a new era of colour photography had arrived. All colour film in use today evolved from these pioneering products.

Vacuum diode [1904, John Ambrose Fleming]

The first electronic device was the vacuum diode, a sealed air-evacuated tube with two metal electrodes, invented by Sir John Ambrose Fleming, professor of electrical engineering at University College, London.

In 1883, Thomas Edison sealed a metal wire inside a light bulb and discovered that a bluish glow could be seen between it and the nearby filament. He had neither explanation nor use for it, but in 1897 Joseph John Thomson, an English physicist, worked out that the glow was due to the passage of tiny particles carrying a negative charge; he had discovered the electron.

In 1904, Fleming substituted a metal plate for Edison's wire and discovered that the electrons travelled to the plate only when it was carrying a positive charge. It meant that the device converted (or rectified) alternating current to direct current. Fleming called his two-electrode device ("diode") a thermionic valve, as it allowed current to flow only in one direction, a characteristic that enabled it to detect radio waves.

In 1906, Lee De Forest, an American inventor, added a grid of fine wire between the filament and plate to invent the triode. He found a small charge on the grid could be used to amplify or reduce a large flow of electrons between the other two electrodes. This was the first amplifier.

Vacuum tube diodes and triodes were at the heart of thousands of electronic devices that followed, such as radios, amplifiers, televisions, long-distance telephony and the first digital electronic computers, until they were replaced in the 1950s by the transistor.

Windscreen wipers [1905, Mary Anderson]

A standard fixture on all cars today, the wiper blade wasn't invented until 20 years after the motor car, perhaps because many early vehicles were open-topped, so drivers didn't go out much in bad weather.

On a trip to New York City, Mary Anderson of Alabama noticed how her driver struggled to remove the snow and ice from his windscreen. She came up with the idea of a wiper operated via a lever inside the car, and patented the device in 1905. She never went into production with it but by 1913 it was standard on American cars.

Electric washing machine [1907, Alva Fisher by James Dyson]

Doing the week's washing used to be a major event for my parents' generation, taking up the best part of a day. I can remember the hard physical effort, lifting heavy, sodden clothes with wooden tongs, wringing them out, steering them through a mangle and finally hanging them out to dry, British weather permitting, of course.

Designers of the modern washing machines faced two key problems. First, the density of water (a sink-full weighs more than 20 kg) means that the machines have to be pretty powerful, especially if the water is going to be extracted by spinning. Then there is the huge heat capacity of water, which means that several kilowatts of power are needed to heat enough to wash a single load of washing in a reasonable time.

The American engineer Alva Fisher is generally credited with making the world's first electric washing machine, the Thor, in 1907, while the American inventor Vincent Bendix claims credit for the first automatic washing machine, which washed, rinsed and dried without much outside intervention.

These machines didn't really take off until the 1960s, first in the form of "twin tubs", which were then eclipsed by automatics. Since then, washing machines have been growing in sophistication, able to give decent results at the lower washing temperatures that environmental regulations demand of manufacturers. Spin driers develop hundreds of g-force to dry clothes, and the whole operation is controlled by microprocessors.

The general view is that washing machines have freed us from drudgery, but by the time you have sorted the washing, put it in, taken it out, hung it up, ironed and folded it, it's tempting to think we'd be better off handing it to a laundry.

Caterpillar tracks [1907, England]

Several patents were registered for caterpillar tracks long before anybody constructed a vehicle that could run on a continuous belted tread. The earliest, for "a portable railway, or artificial road, to move along with any carriage to which it is applied", was filed in 1770 in England by a Richard Edgeworth.

Benjamin Holt, the owner of a California heavy-equipment company that later became the Caterpillar Tractor Company, is often credited with making the first caterpillar tractor in 1904, but all he did was to attach tracks, in distinct blocks, to the rear wheels of his steam tractor.

The first caterpillar tractor to use a continuous series of separate links joined by lubricated pins was invented by David Roberts and built by the firm of Ruston Hornsby and Sons. This petrol-driven tractor was demonstrated to the War Office in 1907 but they showed no interest. Hornsby sold the patent rights to Holt and the caterpillar was forgotten until it re-emerged on the tank towards the end of the First World War.

Armour had been fixed to trains by the time of the Boer War when the War Office considered armoured tractors for use as "mechanical horses". In 1900 the first armoured car was built. Twelve years later De la Mole, an Australian inventor, submitted to the War Office a design for an armoured vehicle with caterpillar tracks. It was rejected. But by 1915 the Great War had become bogged down.

What was wanted was something that could crush obstacles, cross trenches and protect the troops. Winston Churchill, the First Lord of the Admiralty, realised that some form of armoured vehicle was the answer and set up the Landships Committee to examine ideas. In July 1915 an armoured car body was fitted on to the chassis of a tractor. It was not a success in trials, but Churchill pressed ahead.

The first tank, called "Little Willie", designed by Major W.G. Wilson of the Royal Naval Air Service and William Tritton, an engineer from Lincoln, was top heavy and its length was insufficient to cross a German trench. Wilson and Tritton then came up with the classic lozenge-shaped caterpillar track on Big Willie, or Mother as it was later called, and the British Army ordered 1,000.

To disguise their identity, the vehicles were shipped to France described as "tanks", and the name stuck. There were two versions, one with two six-pounder guns, the other with machine guns. The first time tanks showed their worth was in the Battle of Cambrai in November 1917, when nearly 400 of them led two platoons of infantry on a six-mile front that penetrated further than any previous attack, taking 7,500 prisoners and 120 guns.

The obvious advantages of the tank were seen by other countries and there were great developments before the Second World War, when the German Panzers demonstrated how effective tanks could be when used in conjunction with aircraft.

Coffee filter [1908, Berlin]

Europeans knew nothing about the intoxicating pleasures of drinking coffee until the 16th century. For the next 300 years, coffee fanatics - J. S. Bach and Immanuel Kant among them - would find their enjoyment tainted by a thick, gritty residue in their final sips.

The gritty coffee-drinking experience was revolutionised on July 8 1908, when the Berlin Patent Office received a registration from a Dresden housewife. Melitta Bentz had invented a prototype for the first coffee filter, with the aid of a piece of her son's blotting paper and a perforated tin can. With her husband, Bentz set up a company, called Melitta, devoted to the filter's development, and in 1936 patented the conical filter that is still used today.

The short, sharp hit of the espresso had its origins some 200 years earlier in metal jugs that, when heated on a stove, forced boiling water through ground coffee, but it took a succession of false starts for a mechanical espresso maker to be successful.

At the Paris Exposition in 1855, Edward de Santais showed a complicated prototype espresso machine with four chambers that forced steam and hot water through ground coffee. An Italian, Luigi Bezzera, patented the first commercial espresso machine, based on de Santais's design, in 1901. Bezzera was an inept businessman and his rights were bought in 1903 by Desiderio Pavoni, who produced the espresso machine in quantity from 1905 in his factory in Italy.

The best espresso was found to be made at a temperature of 90C and a pressure of about 150 psi (between nine and 10 times atmospheric pressure). In 1938, M. Cremonesi, another Italian, designed a piston-type pump which forced hot, but not boiling water through the coffee. This was installed in Achille Gaggia's coffee bar in Italy. Gaggia saw the value of the design and set up in business in 1946 selling his own version of the Cremonesi machine, called the Gaggia, with great and continuing success.

Neon lamp [1910, Georges Claude]

The vivid red glow of neon energised with a strong electrical current was a sensation at its first public showing, the Paris Motor Show in 1910. It had been discovered eight years earlier by the French engineer Georges Claude, who was the first to try the inert gas in a lamp.

Claude set up a company, Claude Neon, to market the invention around the world. Advertisers soon realised that the light was highly visible during the day, and the glass tubes could be shaped to form words and pictures.

The vibrant night landscapes of American cities were first lit by neon in 1923, when Claude started exporting his tubes. By using different gases more than 150 different colours can be produced.

Kitchen mixer [1910, Hamilton, Beach and Osius]

The first patent known to have been made for a mixer belongs to L.H. Hamilton, Chester Beach and Fred Osius. In 1910 the trio formed the Hamilton Beach Manufacturing Company to make a mixer that looked similar to machines used to make milk shakes today.

The first domestic version of a multi-purpose mixer with several attachments is said to be the KitchenAid, invented by Herbert Johnson, an engineer, and sold to the US Navy in 1916 for kneading dough. It was the first mixer in which the beater and the bowl rotated in opposite directions, and it sold for $189.50 for home use from 1919. A more affordable and portable version was introduced in the 1920s and has since become a "design classic".

In 1922, Stephen J. Poplawski invented the blender, when he became the first to put a spinning blade at the bottom of a container. Poplawski, a drugstore owner, used his invented appliance to make soda-fountain drinks. In 1935, Fred Waring collaborated with Fred Osius to improve on Poplawski's idea to make the Waring Blender, which is still sold today.

Stenotype machine [1911, Ward Stone Ireland]

The problem of how to record speech in courtrooms and conferences quickly, quietly and accurately taxed engineers and inventors throughout the latter part of the 19th century.

Ward Stone Ireland, an American court reporter and shorthand enthusiast, came up with a machine in 1911. He called it the Ireland Stenotype Shorthand Machine and it was an instant success. Weighing in at five kilograms, it had a fully depressible keyboard, making it possible for typists to record whole words and numbers at a stroke and in tests it was proved faster than the most accomplished shorthand writers of the day.

Ireland founded the Universal Stenotype Company, which went on to improve the machine, making thousands of models for the American government during the First World War. But the government didn't pay for the Stenotypes that they ordered and the company was bankrupted.

Stenotype machines now used have 22 keys (some letters are represented by combinations of keys) that print on to a thin strip of paper. By using abbreviations, stenographers can type up to three words in a single stroke.

Brassière [1913, Mary Phelps Jacob]

For centuries the female breast has endured discomfort in the pursuit of the changing fashions for an ideal silhouette.

A "breast supporter" was patented in 1893 by Marie Tucek, a device involving separate pockets for the breasts and straps with hook and eye closures. It did not catch on.

The first practical, popular brassière to receive a patent was invented by the New York socialite Mary Phelps Jacob in 1913. Jacob had bought a sheer silk dress and didn't want to wear the whalebone-stuffed corset of the period beneath it.

She came up with an alternative: two silk handkerchiefs joined with pink ribbon. It freed a generation of women from the confines of the corset, which had reigned supreme since Catherine de Medici's ban on thick waists at the court of her husband, Henri II of France, in the mid-16th century.

Jacob patented the invention in 1914 and went on to sell it under the name Caresse Crosby. It didn't make her fortune: her business collapsed and she sold the rights on to Warner Brothers Corset Company for $1,500. Over the following 30 years they made $15 million from the New York woman's inspired improvisation.

In 1928, when flappers' fashion dictated that women should be flat-chested, Ida Rosenthal, a Russian immigrant, came up with the idea for grouping women into alphabetical categories according to cup size.

Ecstasy [1913, Merck]

When the German pharmaceutical giant Merck registered the patent for 3,4 methylenedioxymethamphetamine (mdma) in 1913, its destiny as the signature drug for the "Ecstasy Generation" 70 years later was impossible to predict. Merck decided against marketing the drug, developed primarily as an appetite suppressant.

In 1967 the fringe biologist Alexander Shulgin, fascinated by the power of mind-altering chemicals after receiving morphine for a hand injury, rediscovered mdma. Shulgin was the first known human to have tried it, recording its effects - along with 179 other psychoactive drugs - in his landmark publication pihkal (Phenethylamines I Have Known And Loved). Entry 109, mdma, was described as the closest to his expectations of the perfect therapeutic drug.

MDMA works by inhibiting the uptake of the serotonin, a brain chemical that helps control depression, anxiety, memory disturbance and other psychiatric disorders. Derived from an organic compound, Ecstasy can be made only in the laboratory in a complex process. It acts as an empathogen-entactogen, increasing communication and empathy and promoting a sense of well-being. Between 1977 and 1985, when it was outlawed by the US Drug Enforcement Agency , mdma was used experimentally on as many as half a million people to treat clinical depression, schizophrenia and even in marriage guidance.

Zip [1913 Gideon Sundback by James Dyson]

With an ingenious arrangement of teeth, each machined to tolerances of a few 10-thousandths of a centimetre, with its versatility and ubiquity, I should be hailing the zip as a brilliant invention. But I can't. It jams, it corrodes, it falls to pieces, and those teeth can convert any man into a boy soprano in a split-second.

Certainly, it's clever. But it has been asked to do more than it should. When Whitcomb Judson, a mechanical engineer from Chicago, showed his patented "clasp locker" at the Chicago Worlds Fair of 1893, it was intended as a replacement for couplings on high boots. (Elias Howe, famed for inventing the sewing machine, was granted a patent for his zip-like "automatic, continuous clothing closure" in 1851, but never commercialised it.)

Judson's system failed to catch on, and he sold only 20, all to the US mail service as bag fasteners. It was the Swedish engineer Gideon Sundback who, in 1913, got the zipper to work, by trebling the number of teeth and inventing a machine to stamp them out and fix them on a flexible material.

The credit for making the zip a commercial success usually goes to the American company BF Goodrich, which in 1923 incorporated the zip into rubber boots. The company also gave the fastener its name, after the noise that it makes as it opens and closes.

The zip found its way into ever more garments, with one magazine in 1925 trilling: "no fastening is so quick, secure or popular as the zipper". Someone eventually thought it would be a great idea to replace the buttons on the flies of men's trousers with a zip, and claimed that it eliminated the risk of embarrassment through failing to do one's flies up. It is a claim that will no doubt be greeted by any man with total derision.

Sonar [1916, Military scientists]

At the outbreak of the First World War, the Admiralty in London was slow to realise the threat posed by the U-boats of the Imperial German Navy. Soon thousands of tons of shipping were being sunk and lives lost, culminating in the torpedoing of the liner Lusitania in 1915, on which 1,198 died.

Something had to be done. By July 1915 the Admiralty had established the Board of Invention and Research, with luminaries such as the nuclear physicist Ernest Rutherford giving advice. The section of the board responsible for submarines and telegraphy was given a great deal more money for research than other departments. The use of dowsing-rods was tried out, as was the possibility of training submarine-spotting seagulls and sea lions.

The Anti-Submarine Division of the Admiralty, together with American and French scientists (notably the physicist Paul Langevin) came up with the first successful submarine detection system in 1916: a line of specialised microphones, called hydrophones, that were towed behind a ship. This was a passive system; it emitted no pulses of sound. Operators listened for sub- marine noises and calculated a bearing to guide attackers on to the enemy. The first U-Boat to be detected and sunk in this way was the UC3 on April 23 1916.

British sound detection systems were named asdic (Anti Submarine Detection and Investigation Committee). Work was carried out on "active" asdic systems which emitted a characteristic "ping" sound when an enemy sub reflected an echo. Anti-submarine warships used the ping to calculate the range, bearing and depth of the sub before an attack with depth charges. Active asdic helped to win the underwater war.

In America such systems were dubbed Sonar (SOund Navigation And Radar) in 1942 by the acoustic scientist, F. V. Hunt. The term did not catch on in the Royal Navy until the late 1950s.

Hairdryer [1920, Germany]

The electric hairdryer was invented in Germany in the early 1920s, when compact electric motors developed for use in vacuum cleaners became small enough to fit into a reasonably compact handheld unit. The technology was simple: the motor turned a fan which blew air over an electric heater - usually current-resisting nickel, iron and chrome alloy wire on a mica or asbestos board. Early models were large, heavy and unwieldy. They incorporated large magnets with chrome-plated steel or nickel for the housing and solid wood handles.

The invention of Bakelite, the first synthetic plastic, liberated the hairdryer from its weighty origins and made it a much safer appliance: thermoset plastics would not distort under heat, and, more importantly, unlike the metal housings, they did not conduct electricity in the event of a short circuit.

The use of plastics also turned the hair dryer into a fashion accessory as models in walnut-effect brown, ivory, bottle-green, jade-green and red also became available. After the Second World War, induction motors replaced the heavy brush motors and the hair dryer became smaller, lighter and almost silent.

Sticky plaster [1920, Earle Dickson]

In 1920, a newlywed couple, Josephine and Earle Dickson, were living in New Jersey. Every evening, the accident-prone Josephine would have dinner on the table for Earle's return but she would also have several cuts or burns on her fingers.

Without an adhesive bandage, Josephine had no easy way of bandaging her own cuts, so Earle would cut pieces of adhesive tape and cotton gauze to make a bandage for each wound.

Finally, after several weeks of kitchen accidents, Dickson prepared ready-made bandages by placing squares of cotton gauze at intervals along a strip of surgical tape. He covered them with textured crinoline. Now all Josephine had to do was cut off a length of the strip, peel away the crinoline and wrap the ready-made bandage over her cut.

Dickson worked at Johnson & Johnson, who by the 1920s had become successful selling baby powder and sterile bandages. He mentioned his invention to his superior, who was unimpressed until Dickson demonstrated that he could easily apply a bandage with one hand to himself. Soon the first adhesive bandages were being produced and sold under the Band Aid trademark.

The first handmade Band Aids came in sections 7cm wide and 45cm long and did not sell well. But by 1924, Johnson & Johnson had developed a way of manufacturing several sizes by machine, and the sticky plasters caught on. Since then more than 100 billion have been made.

Submachine gun [1920, John Thompson]

The usefulness of machine guns on the battlefield was limited by their weight and size. They would be much more useful if they were light enough to be handled by one person. The first step to the submachine gun was to use smaller, lighter, pistol cartridges, first seen on the Villar Perosa, an Italian gun patented in 1915, which fired 9mm ammunition so fast it could empty its magazine in two seconds.

The Villar Perosa had two barrels and a double handgrip and was sometimes mounted on a tray hung around the neck. In 1918, the Germans introduced the Bergman MP18, which used 9mm Luger bullets loaded and cocked by the force of the explosion of the previous round. It had a shoulder stock and could therefore lay claim to being the first submachine gun.

However, many regard the Tommy gun as the first submachine gun. The American Auto-Ordnance Company, under General John Thompson, who apparently first used the title "submachine gun", developed it in the early 1920s.

The Tommy gun used .45 calibre ammunition designed for Colt pistols, which it fired at a rate of 800 rounds a minute. The first war in which submachine guns were used extensively was the Spanish Civil War of 1936-39. The Allies and the Germans were armed with submachine guns in the Second World War, the British having developed a simple model, called the Sten. Today, the Israeli-made Uzi, the Koch MP 5 and Heckler (both German) are probably the most widely used.

Robot [1921, Karel Capek]

The term robot dates to 1921, when the Czech playwright Karel Capek called downtrodden serfs and slaves "robots" in his play R.U.R. (Rossum's Universal Robots). The play describes a mythical world of leisure, with lucky humans able to enjoy lives of utter pleasure, waited on by machine servants. Paradise turns to purgatory, however, as the robots bring unemployment and cause society to fall apart.

Robotic technology has developed in a benign way. The first commercially available robot was devised in America in 1956 by George C. Devol and Joseph F. Engelberger. Called "Unimates", the robots worked first in a General Motors engine plant. The two engineers formed a company, Unimation, which still makes industrial robots.

Nowadays, millions of robots are used for mundane tasks in factories and even to investigate the surface of Mars, as Nasa's Sojourner did so spectacularly in 1997. However, few conform to the archetypal image of a mechanical humanoid. Making a machine walk upright on two legs remains a tough task for robot designers; nevertheless the designers still strive to make anthropomorphic machines, as much for the engineering challenge as anything else.

Of those robots that do walk on legs, such as the autonomous vehicles that examine pipelines on the oceans' beds, most have six or eight legs, like a spider.

Insulin [1921, Frederick Banting and Charles Best]

Inside our bodies, the digestion of carbohydrates results in the production of glucose, known as blood sugar. The amount of glucose present has to be closely controlled. The hormone that regulates this process is called insulin and it is produced in the pancreas.

Too much glucose causes the condition known as hyperglycaemia. In itself, this is not lethal, but it can be a symptom of a disease, diabetes mellitus. People with diabetes have a restricted production of insulin, and the increased levels of blood sugar cause the body to produce poisons, which, without treatment, will result in death.

It was Joseph von Mering and Oskar Minkowski in 1889 who discovered that the pancreas controlled the glucose metabolism. By removing the pancreas of live dogs they could immediately cause the onset of severe diabetes. Although this inferred the existence of insulin, it proved difficult to isolate because digestive enzymes quickly destroyed the hormone.

In Toronto in 1921, following repeated attempts to extract insulin, Sir Frederick Banting and Charles Best discovered that by tying off the pancreatic ducts of a live dog they could cause the pancreas to produce certain cells. When injected into diabetic dogs these cells cured all symptoms of diabetes. This led to the isolation of insulin.

The work of Banting, Best, von Mering and Minkowski, meant that diabetics could live a reasonably normal life, either by observing a carefully formulated diet or by having periodic insulin injections.

Quantities of animal-derived pancreatic tissue were required to produce insulin. But by 1981 a process was discovered to produce it artificially. This became the first protein produced by genetic engineering to be used to treat a human disease.

Hearing aid [1923, Marconi Company]

Cupping a hand around the ear can improve hearing by five per cent. In Victorian times, a wide range of trumpets and horns were popular, while hirsute gentlemen could take advantage of an under-beard listener and top hats were available with discreet earpieces.

Until the advent of electrical microphones and amplification, however, there was no help for the very deaf. In the 1890s Alexander Graham Bell may have been trying to build a hearing aid when he stumbled/p.20 p.18/on the invention of the telephone. His carbon microphone was capable of turning sound waves into electrical impulses, which were then amplified and turned back into sound at the receiver's end.

The major problem was the lack of suitable batteries. The Marconi Company in Britain came up with what they claimed was the first practical portable hearing device in 1923. Called the Otophone, it used a carbon microphone and a valve amplifier to channel sound to the wearer. Marconi were nearly there - but, with batteries, it weighed 7 kg.

A machine made by A. Edwin Stevens in 1935 was a breakthrough; it used lightweight valves and, weighing 1 kg, it could be worn around the neck. The invention of the transistor shrank aids further in the 1950s. Now, in the digital age, selected frequencies can be amplified, giving a much better quality of sound.

Frozen food [1924, Clarence Birdseye]

The first person to examine whether freezing food might delay its deterioration died in the process. In March 1626, Francis Bacon, lawyer, Member of Parliament, wit and philosopher, was passing Highgate in north London. Observing the snow outside his carriage, he wondered if cold might delay the putrefaction of living tissue. He stopped his carriage immediately, bought a hen, and with his own hands, stuffed it with snow. But he was seized with a sudden chill, which turned to bronchitis, and he died at the Earl of Arundel's house nearby on April 9.

Some three centuries later, Clarence Birdseye, an American businessman, developed Bacon's speculation into a process for freezing foods in small packages suitable for retailing.

In 1912 and 1916, Birdseye travelled to Labrador in northeast Canada to trade fur. He noticed the natives froze food in winter because of the shortage of fresh food. The combination of ice, wind and temperature almost instantly froze fresh fish straight through. When the fish were cooked and eaten, they were scarcely different in taste and texture than they would have been if fresh.

Birdseye, a former government naturalist, realised the fish froze too quickly for ice crystals to form and ruin their cellular structure. Inspired by what he had seen, he experimented with frozen foods on his return to New York. In 1924 he founded the General Seafoods Company, having patented a system that packed fish, meat or vegetables into waxed-cardboard cartons that were flash-frozen between two refrigerated metal plates under high pressure.

Five years later he began selling his quick-frozen foods, which made him wealthy. He introduced refrigerated glass display cases in 1934 and leased refrigerated railway boxcars to distribute his frozen products throughout America.

Birdseye's invention significantly changed eating habits, but he was not a one-trick pony. He held nearly 300 patents, covering infrared heat lamps, a recoilless harpoon gun for whaling, and a method of removing water from foods.

Geiger-Müller counter [1925, Geiger and Müller]

Many who grew up during the Cold War will be familiar with a nagging feeling of doom whenever the crackling, insistent din of a Geiger counter filters over the radio or television. It was the soundtrack of the nuclear paranoia that enveloped much of the world in the post-war years.

The Geiger counter is, in fact, an extremely useful measuring device - able to scan the environment for background radiation of many different kinds. The brilliant German physicist, Johannes Wilhelm Geiger, gave his name to a machine he devised to prove his own ideas about atomic science.

On finishing his PhD in 1906 at the University of Erlangen in Germany, he went to work for Ernest Rutherford at the University of Manchester. Rutherford was engaged in his pioneering work about the nature of nuclear matter.

Geiger thought that gases would conduct electricity only when their atoms had been ionised - or split up into free electrons or ions. Radioactive materials emit such free electrons and ions and, in Manchester, he set out to build a machine capable of sensing these particles.

At the heart of the first counter, completed around 1911, Geiger had a small metal tube containing a thin wire between two electrodes. The assembly was sealed into a gas-filled glass bulb. A high-voltage current passed through the wire between the two electrodes. Free ions or electrons passed into the tube and interfered with the ionised gas around the wire, creating pulses of current. These were recorded or used to drive a loudspeaker, hence the familiar sound of the Geiger counter.

This first version of the Geiger counter was used to identify alpha particles as the nuclei of helium atoms, a vital step in Rutherford's determination of the nature of the atom.

The next year, Geiger returned to Germany, developing the counter with another physicist, Walther Müller.

In 1925, the pair produced an instrument capable of detecting a wide range of radiation and particles, such as electrons and ionising electromagnetic photons, the matter-penetrating radiation that provokes such fears at the tick-tick sound of the counter.

Liquid-fuel rocket [1926, Robert Goddard]

Born in 1882 in the small city of Worcester in Massachusetts, Robert Goddard was inspired by Jules Verne and H.G. Wells about flying to the moon. He developed an instinctive feel for pyrotechnics and was intrigued by the black powders that provided the chemical violence for TNT. But as professor at Worcester Clark University, he discovered that to launch a rocket any distance would need more sheer power than conventional solid fuels could afford.

If the fuel was to explosively expel itself from a rocket tail at a high enough speed to push the rocket forward (the Newtonian basis for all of rocket science) it needed energy to spare, with more fuel to sustain flight.

Goddard knew he needed the thrust of a vast amount of fast-burning fuel to overcome the weight of a moon rocket of any reasonable size. Static solid fuels were hard to control and lacked efficiency, but a liquid fuel, such as hydrogen, might be a different matter. He believed that if hydrogen could be piped into a combustion chamber sufficiently fast and burnt with liquid oxygen, enough power would be produced to get to the moon.

He used solid-fuel rockets to refine his techniques and prove basic principles. By 1915 he had taken solid-fuel rockets to their limits by carrying simple instruments to investigate the atmosphere. At the same time, for the war effort, he invented the bazooka, which was taken up by the US Army shortly before the end of the war.

Goddard first published his work in a 1920 report to the Smithsonian Institute entitled A Method of Reaching Extreme Altitude. It concluded that the best way to test rockets was to fly them to the moon and to use explosive flash-powder to show their arrival.

The paper was picked up by the New York Times, which gave him a pasting. As anyone knew, the January 13 editorial explained, travel to the moon was impossible, since without an atmosphere to push against, a rocket could not move so much as an inch, and Goddard lacked "the knowledge ladled out daily in high schools".

Goddard was furious and he immediately embarked on a quarter-century of research. It began with a first test flight on March 16 1926. Having solved the problems of fuel delivery to the combustion chamber and stabilising the rocket's course, he built a top-heavy three-metre missile called Nell. A team of four horses wheeled it out to his aunt Effie's farm where his wife took notes. An assistant lit the oxygen-gasoline mix using a blowtorch on a long stick, and for a short moment the rocket did nothing. Then it leapt, screaming, into the sky at 60 mph, climbing to a modest 14 metres before crashing in a cabbage patch.

Still smarting from the press attacks, Goddard kept quiet about his trials, but the launch of a fourth rocket brought attention. "Moon rocket misses target by 238,799 miles" read one headline.

More importantly, however, Charles Lindbergh, the transatlantic aviator, was impressed, and he introduced Goddard to Harry Guggenheim, the millionaire financier who provided sufficient funds for Goddard to move to Roswell, New Mexico, where for nine years in arid scrubland Goddard continued his research in great privacy.

Few took any interest in his work, but now and then German engineers would contact him with technical questions. In 1939, with the outbreak of war, Goddard became concerned and he contacted the US Army to show them movies of the Nell rockets and their potential for destruction. But the Army paid no attention to his warnings. Five years later, the first German V-2 rocket blasted off for London.

When Goddard finally had a chance to examine a V-2, he recognised his own handiwork. The Nazis had taken his papers, read his 200 patent applications and twisted his peaceable Nells into weapons of war.

Goddard died of throat cancer in 1945, never seeing his dreams of space travel come true. His work was taken up by American and émigré German scientists to produce the Redstone rockets that sent the first Americans into space and, in 1969, placed man on the moon. It prompted an apology from the New York Times: "Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th century, and it is now definitely established that a rocket can function in a vacuum as well as the atmosphere. The Times regrets the error."

Pop-up toaster [1926, America]

Bread has been toasted to prolong its edible life since Roman times - tostum is Latin for roast or burn - but, for thousands of years, toasting was accomplished simply by holding the bread close to a flame, often with a fork or tongs.

The first electric toaster, invented in 1893 by Crompton and Co, a British company, became possible when current-resisting elements from electric fires and irons were built into a unit with a wire cage that could sit safely on the table. Its appeal was immediate.

The first refinement came in 1918, when sprung doors were added. Provided they were opened with a snappy movement, these doors turned over the toast automatically, but still required a watchful eye to prevent the toast burning. That changed in 1926, with the pop-up Toastmaster, an American invention.

The 1930s saw an eccentric British version ejecting the toast sideways and pop-up toasters did not become popular in Britain until Morphy-Richards introduced a model in 1948.

Equally important was the invention of sliced bread in 1928 by Otto Frederick Rohwedder, an American jeweller who made a machine that wrapped bread immediately after slicing it, keeping it moist and fresh.

Videophone [1927, Bell Laboratories]

Despite its obvious appeal, the videophone has failed to catch on significantly since it was invented in 1927 - because videophones have to be bought in pairs for the caller to be able to see the person they are calling and, even then, the pictures are jerky and fuzzy.

The American telecommunications company AT&T dem-onstrated the first experimental videophone, but it worked in only one direction. A two-way system was unveiled in 1930, linking AT&T's head office and its research department, Bell Laboratories, both in New York.

In 1956 Bell demonstrated its "Picturephone" system, but it needed up to 125 telephone circuits to produce a reasonable picture. By 1968 Bell had perfected a system that required a relatively narrow bandwidth and it went into service in 1971, but was eventually discontinued.

It wasn't until the early 1990s that phones with moving pictures became a practical reality, the key development being digital image processing.

Quartz timekeeping [1927, Warren Marrison]

Wearing a watch on the wrist became fashionable for women following the late-19th-century craze for cycling, when leather wrist "converters" were designed so that women could securely hold their small fob watch on the wrist. The fashion soon outgrew the need of an accompanying bicycle and spread to men, who overcame their initial hostility to wristwatches. Soldiers found them useful in the First World War.

In 1925, Hans Wilsdorf, a German-born English national living in Switzerland, purchased a Swiss patent for a waterproof winding button, and a year later the first successful waterproof watch, the Rolex Oyster, was born. Two years earlier, John Harwood, an Englishman, pat-ented a system of automatic winding that led, in 1928, to a successful automatic wristwatch.

However, the most significant development in modern watchmaking happened in 1927, when Warren Marrison, a Canadian-born engineer working at the Bell Telephone Laboratories in America, built the first quartz-crystal controlled clock. The quartz in the Marrison clock vibrated 50,000 times a second; by using a combination of electronic and mechanical gearing at a ratio of three million to one, this oscillation was used to move the second-hand through one rotation every 60 seconds. Capable in observatory conditions of losing only one second in 10 years, quartz technology produced a leap in accuracy, but needed the corner of a small room to house the workings.

Research into electric-powered watches began in the 1940s and the Hamilton Watch Company of America launched the first, the Ventura, in 1957. It was a tremendous success and other manufacturers in France and Switzerland soon followed. These new electric watches were still part mechanical and culminated in the first quartz wristwatch. The first 100, made by Seiko, went on sale on Christmas Day 1969. Advances in miniaturisation technology allowed the quartz workings to be squeezed into a watchcase, a feat that cost the consumer $1,250 a piece at the time, the same as a medium-sized car. Within 20 years quartz watches would be given away free at petrol stations with a tank of petrol.

In 1972, the Hamilton Company developed the first all-electronic wristwatch, the Pulsar. It had flashing red light emitting diode (LED) digits in the place of hands on its dial. Its main disadvantage was that a button had to be pressed to read the time.

By 1977, permanently visible liquid crystal display (LCD) had become the most popular way of showing the time. Sufficiently powerful small batteries were a big problem with the early models and much research went into their improvement. Watches with small electric generators powered by wrist movement were invented, as were watches powered by body heat. Solar-powered watches appeared in 1973, and battery design has improved so that many can run for two years or more.

In 1990, Junghans produced a wristwatch controlled by super-accurate caesium atomic clocks in Germany, England and America. It is accurate to one second in a million years, as long as the watch can receive a radio signal from the atomic clock.

Antibiotics [1928, Alexander Fleming]

One of the most important advances ever made in medicine began with a Monday morning clean-up in a hospital laboratory in central London.

On September 3 1928, Alexander Fleming, a professor at St Mary's Hospital Medical School, was sorting through a heap of glass plates coated with staphylococcus bacteria as part of a research project. Fleming noticed one of the plates had mould on it: spores of Penicillium notatum had landed on the plate. "That's funny," said Fleming to a colleague, pointing to a strange ring around the mould that seemed to be free of staphylococcus.

Many scientists would probably have thrown the plate away. But Fleming had a long-term interest in ways of killing bacteria, which are responsible for a vast range of diseases from food poisoning to the Black Death. The bacteria-free region around the Penicillium suggested it was exuding some substance that was killing the staphylococcus.

Fleming made a careful drawing of what he saw and then set about trying to find out more about the mystery substance. Filtering some of the mould, he discovered that it killed some other bacteria apart from staphylococcus, and could be given to mice and rabbits without side-effects.

However, Fleming's investigation of the mould's medical potential for treating human diseases was not encouraging, and within a year he had moved on to other things. A decade passed before Howard Florey and Ernst Chain, an Australian pathologist and a German biochemist working together at Oxford University, made the key breakthrough of isolating the bacterium-killing substance produced by the mould: penicillin.

In 1941, Charles Fletcher, a doctor at Oxford's Radcliffe Infirmary, happened to hear about their work, and told them about one of his patients, a policeman named Albert Alexander who had scratched his face on a rosebush. Both streptococci and staphylococci had invaded Alexander's body, and he was close to death. Fletcher gave Alexander 0.2 grams of Florey and Chain's penicillin, followed by smaller doses every three hours. Within a few days, the

patient underwent an almost miraculous recovery and his wounds began to heal up. Tragically, Fletcher did not have enough penicillin to finally rid his patient of infection, and the bacteria fought back, killing the patient a few weeks later.

Even so, it was an impressive demonstration of the powers of penicillin. The problem now was to mass-produce the substance so that more patients could benefit. Florey succeeded in persuading American drug companies to work on the problem, and by the time of the Normandy landings in 1944 there was enough of the "wonder drug" to treat all the severe cases of bacterial infection that broke out among the troops.

For their brilliant work in turning a chance discovery into a life-saving drug, Florey and Chain shared the 1945 Nobel Prize for Medicine with Fleming. Today, almost half a century later, penicillin-based antibiotics are still the safest and one of the most widely used in medicine.

Iron lung [1928, Philip Drinker]

For centuries the polio virus was a feared killer, especially of young children. Ingested via contaminated food or water, the virus targets the nerves in the spine responsible for movement. Paralysis can follow within hours, and if the virus reaches the nerves responsible for respiration, victims are unable to breathe, and slowly drown on their own secretions.

Doctors had long recognised that they might be able to spare many polio victims this terrible fate if a way could be found of keeping the lungs working until the nerves recovered from infection.

In 1926 the Rockefeller Institute in America set up a commission to investigate this possibility. One of its members, Harvard physician Philip Drinker, had an idea after talking with his brother, who was studying the respiration process in cats. To measure the volume of air breathed in, Drinker's brother had devised a sealed box, the air pressure within being recorded. As the cat inhaled, its extra volume caused a pressure rise, and vice versa.

Drinker realised that by flipping this process around - using pressure to control lung-volume - he could maintain respiration in paralysed polio victims. He had a craftsman build a sealable box, with the air pressure being controlled by a vacuum cleaner. In 1928, the first patient, an eight-year-old girl on the brink of death from respiratory failure, was put in the box. Within a few minutes she was conscious, and asking for ice cream.

The girl later died of pneumonia, but the principle had been proved. Drinker's machine, dubbed the "iron lung", went into production in 1931. Iron lungs went on to save the lives of countless thousands. Today sophisticated portable ventilators have largely replaced them, but some still remain in use.

Artificial life [1929, John Bernal]

The Irish crystallographer John Bernal anticipated in 1929 the possibility of machines with a lifelike ability to reproduce themselves. He wrote of this "postbiological future" in The World, The Flesh and The Devil: "To make life itself will be only a preliminary stage. The mere making of life would only be important if we intended to allow it to evolve.''

Two decades after Bernal's vision, the great computer pioneer John von Neumann performed the first demonstration of the possibility of artificial life, in his work on self-reproducing automata. Though he conceived his automaton some years before the structure of the genetic blueprint (DNA) had been unravelled, he laid stress on its ability to evolve.

Modern computers have brought von Neumann's realisation of the logical nature of life closer to reality. Some examples of weak "ALife" forms were born during Core Wars, a game played by computer addicts. The idea was to create programs that compete against each other for processing time and space in computer-memory - rather like animals competing for food and territory. Now there are unintended versions of Core Wars, better known as computer viruses, existing in computers around the world.

Core Wars programs and computer viruses are capable of self-replicating, but not of evolving in an open-ended fashion. For there to be any chance of creating genuine artificial life within a computer, ways must be found to introduce novelty by mutations and then to select the "fittest" objects.

Thomas Ray, while at the University of Delaware, was thought to have created the first example of artificial evolution, based on Darwinian principles, in 1990. His computer contained digital organisms which fought for memory space in the central processing unit just as living organisms might fight for food and energy sources.

Ray's simulation of evolution, which he called Tierra, provided a metaphor for biological complexity, a tool to understand why it is seething with diversity. Computer scientists now "breed" software along genetic models, with the hope that the most efficient software will evolve. And there have even been computer games, such as Creatures, that exploit "ALife" ideas.

The field took a new direction recently when Dr Craig Venter of The Institute for Genomic Research, Rockville, Maryland, reported that he had whittled down the smallest known genetic code - of a simple bacterium - to a bare minimum set of essential genes.

It might even be possible, said Venter, to build the cell from scratch, making a chromosome and adding cell ingredients to see if it "gets its act together and starts replicating."

Radio telescope [1932, Karl Jansky]

In 1932 an American radio engineer, Karl Jansky, was investigating odd interference on transoceanic telephone lines when he received a shock: he encountered a signal, the origin of which he was at a loss to explain. Eventually he found out: the signal was coming from outer space.

His explanation for this phenomenon was that it was being created in space by the interaction of stray electrons and ions. As far as Jansky was concerned, the signals, which sounded like radio static, were emanating from the centre of our own galaxy.

Astronomers the world over were galvanised into action by the findings. In 1937 Grote Reber, an American amateur astronomer, began building the first radio receiver aimed up at space. Reber confirmed Jansky's findings about the direction of the radio waves and he went on to map the whole sky, using his dish to pick up naturally occurring radio transmissions from stars, galaxies, quasars, and other astronomical objects. For six years it was the only purpose-built radio telescope.

But as Europe returned to peace in 1945 there was an upsurge of interest in radio astronomy. Resourceful astronomers in Britain pressed captured German radars and radio receivers into peacetime service. One of these experts was Bernard Lovell, Professor of Astronomy at Manchester University.

Lovell set up his first radio telescope in 1945 at Jodrell Bank, just south of Manchester. But this wasn't enough. He started planning a truly giant radio telescope, consisting of a steerable dish receiver 75 metres (250 feet) across. Construction of the Mark 1a began in 1952 and took five years.

Lovell's project soon hit the headlines in Britain. In October 1957 his team picked up a stream of bleeps that told the world the Russians had become the first nation to launch a satellite into orbit around the Earth.

In the 1960s radio astronomers began for the first time to build up detailed pictures of distant features in space, far beyond the reach of optical telescopes. Pulsars, quasars and exotic phenomena such as Black Holes were discovered.

The Manchester dish, now re-named the Lovell Telescope, is one of the biggest steerable receivers in the world. It is a vital part of the seti project, a worldwide effort to listen out for signs of intelligent life elsewhere in the universe.

Electron microscopy [1933, Ernst Ruska by James Dyson]

Even scientists have trouble accepting some of the tenets of quantum mechanics, the laws of the sub-atomic world - Einstein couldn't bring himself to accept them all. Certainly one of the hardest to credit is that bullet-like particles such as electrons can sometimes behave as if they are waves, like light.

Hard to believe, maybe, but the electron microscope proves it's true. Just as ordinary microscopes focus light waves to magnify images a thousand-fold, the electron focuses the wave-like properties of electrons to produce massive magnification. With wavelengths far shorter than those of ordinary light, electrons can reveal far more detail. A magnification of 50,000 times is routine.

It took less than 10 years for the idea of electrons behaving like waves - put forward by the French theorist Prince Louis de Broglie in 1924 - to be turned into a working electron microscope by Ernst Ruska, an engineer at the Technical University of Berlin.

Ruska began by making an electromagnetic "lens" that brought the electron waves into sharp focus. By 1933, he had found a way of stacking several of these lenses above each other and accelerating electrons to such high energies that their wavelength was around 100,000 times shorter than that of light. Shone through a very thin section of material, the electrons fell onto a photographic plate, where they left a highly magnified image of the material.

This first "transmission electron microscope" could magnify only a few hundred times, but its performance was quickly improved. By the 1960s, electron microscopes were achieving magnifications of several million times, enabling individual molecules to be seen.

But while electron microscopes are excellent for studying inanimate objects, they are useless for studying living, breathing things. Electrons have trouble passing through air, let alone biological tissue. Those vivid, apparently three-dimensional electron microscope images of fleas, bed bugs and the rest are taken by coating their lifeless carcasses with metal, and detecting the electrons reflected off them.

Catseyes [1934, Percy Shaw]

British roads in the 1920s were much more primitive than the smooth well-lit carriageways we expect today. They were mostly unlit: in urban areas moonlight shining off tramlines guided motorists at night - if there were any tramlines.

A young Yorkshire road contractor called Percy Shaw thought he could find a solution to the dangers of driving in the dark. His moment of inspiration came one night when he was driving home across country to Halifax. His headlights caught a cat on a fence and its eyes "lit up" as they reflected the dismal six-volt illumination back to Shaw. He at once realised that reflectors down at the level of the Tarmac could guide motorists safely home.

Shaw set to work, trying to create a reflector out of different combinations of glass lens, mirror and rubber cover to hold the assembly together. By 1934, still only 23 years old, he had perfected the first model, cleverly designed to self-clean the reflectors when the lenses were forced down into the road by a car passing over them.

Transport officials were slow to see the potential of Catseyes: not until the war years, when drivers had to use blacked-out headlights, was the device seen as invaluable. Catseyes were doubly useful in wartime blackout conditions because they reflected light back in a very narrow field of view; there was no danger of their attracting the attention of the Luftwaffe.

In 1947, during the post-war Labour government, junior Transport Minister James Callaghan instituted a massive plan to install Catseyes all over Britain's roads. The basic design is little changed today.

Magnetic recording [1936, Magnetophone by James Dyson]

Storing sound and pictures on tape is one of those inventions that truly strains credulity. How can a thin brown strip of material capture a performance by Glenn Gould with such clarity you can hear him muttering as he plays?

The fidelity of magnetic recording amazed those who first heard it, on the Telegraphone, invented in 1898 by Valdemar Poulson of Denmark. Designed as a telephone answering machine, it worked by applying pulses of magnetism to steel wire at the same frequency as the sound being recorded. To play the sounds back, the process was reversed; the changes in magnetic field stored on the wire were converted back into the original sounds.

Patents for applying magnetic particles to thin paper appeared in America and Germany in 1928. The Magnetophone, invented in 1936, became the prototype for all tape-recording technology. A key figure in its post-war progress was Bing Crosby. All music on TV was then performed live. Keen to avoid the pressure, the singer pushed for (and funded) more use of tape recording.

Engineers at Ampex in America demonstrated their first video recording system in 1956 and the launch of the compact cassette in 1963 by Philips brought tape recordings into every home.

Ballpoint pen [1938, Laszlo José Biró by James Dyson]

There's a world of difference between having a great idea and getting it to work successfully. Take the ballpoint pen...

The "biro" was born in response to the frustrations of Laszlo José Biró, a Hungarian journalist who was all too familiar with the failings of conventional pens, with their leaks and smudges. However, the ink actually used to print his words, he noticed, dried quickly and was much less given to smudging.

Experimenting, Biró found that printer's ink clogged up a fountain pen, so he and his brother Georg developed a new type of nib: a ball-bearing arrangement with the ink acting as a lubricant. They patented it in 1938. Two years later, they fled Hungary for Argentina, and the first commercial version of their pen appeared in 1945, launched under licence by Eterpen of Buenos Aires.

Their next target was the US market, but they were beaten by Milton Reynolds, a Chicago businessman, whose pen design dodged patent problems. Marketed as the Reynolds Rocket pen, 8,000 of the $12.50 pens (equivalent to £70 today) were sold on the first day.

But it took innovative mass-manufacturing methods devised by Baron Bich of France to give the ballpoint its present ubiquity: around 14 million Bic ballpoint pens are sold every day.

Despite its popularity, I've never liked the ballpoint. An ink pen is far more expressive; better still are pencils, which have wonderful precision and smoothness.

Bouncing bomb [1943, Barnes Wallis]

The German anti-aircraft gunners on duty on the calm, clear night of May 16-17 1943 at the Mohne Dam in the Ruhr Valley might have been expecting a quiet watch, after all they had had a quiet war so far. But the gunners were unlucky to be defending one of three dams chosen to be attacked by RAF Bomber Command.

The 19 Lancasters that were launched on the daring raid were carrying a unique weapon: the "bouncing bomb". Barnes Wallis was the British engineer responsible for the imaginative plan. He was convinced that a devastating hammer blow could be dealt to the German war effort if the dams of the Ruhr Valley were destroyed and he conceived the idea of a skipping or bouncing weapon, able to leap over torpedo nets that protected the dams.

Using models at home and at the National Physical Laboratory at Teddington, Middlesex, he refined the idea further: the cylindrical bomb would be spun at up to 500 revolutions a minute just before release to make it bounce across the water. When it finally hit the dam, the spin that remained in the bomb would drive the explosive-packed cylinder down to the base of the dam, where the water would amplify the blast.

Weighing more than 4,320kg, it could be carried only by the four-engined Avro Lancaster, which needed to fly at exactly 220 mph, at 20 metres above the water, releasing the bomb at 150 metres from the target.

It took the personal intervention of Winston Churchill to persuade the War Office to go ahead with the plan. As few Allied aircrews were at that time getting within five miles of their targets in night operations, a special squadron was handpicked from all over the Commonwealth. It was called 617 Squadron.

In a raid later celebrated in the film The Dam Busters, the attackers took off from RAF Scampton in Lincolnshire at 9.30 pm and flew at 30 metres or less across the North Sea towards the Dutch coast. In complete radio silence they screamed over rooftops toward their targets. Three dams were hit, but only two were breached.

Of the 19 Lancasters that left Scampton, 10 returned, 53 aircrew were lost, three were taken prisoner. Wing Commander Guy Gibson, leading the raid, made repeated passes over the dams giving covering fire as his fellow fliers made bomb runs. He was awarded the Victoria Cross; 35 other medals were awarded.

The raid, the first true precision air attack of the war, was an immense propaganda success. Vast tracts of the Ruhr Valley, the industrial heartland of Germany were flooded. More than 1,300 were killed on the ground, including Ukrainian women and children in a prison camp downstream of the dams.

Aqualung [1943, Jacques Cousteau]

The idea of using bottles of compressed air to breathe underwater dates back to at least 1825, when William James, an English engineer, sketched out the basic requirements of an aqualung.

The key problem lay in designing a valve capable of delivering air at the correct pressure to the diver on demand. This was the achievement in 1943 of Emile Gagnon, a Parisian engineer, and Jacques Cousteau, a French naval officer who then used the aqualung to show the wonders of the undersea world to TV audiences of millions.

Kidney dialysis [1944, Willem Kolff]

Working in the municipal hospital of Kampen, in Holland, Willem Kolff, a medical doctor who had previously invented the blood bank, constructed the first, crude artificial kidney in 1944 from wooden drums, Cellophane tubing, and laundry tubs.

The device drew blood, removed toxins that deficient kidneys were unable to excrete, and pumped the cleaned blood back into the patient. Working with comatose men and women, Kolff managed to prolong the lives of his first 15 patients for a few days.

In 1945, a woman Nazi collaborator was brought to him for treatment. Although many in the town wanted to see her dead, Kolff's "haemodialysis" apparatus saved her life. It enabled Kolff to continue developing his dialysis machine, which he shipped free to researchers in England and America after the war. Kolff went on to invent an implantable artificial heart.

And also...

1902

Frank Clarke unveils the first automated tea-maker.

1904 Julius Elster, a German, invents photoelectric cell.

1904 Thomas Sullivan, a New York tea and coffee merchant, uses hand-sewn silk envelopes to invent the tea bag.

1905 Hiram Maxim, inventor of the machine gun, invents the silencer for the gun after working on exhaust silencers for cars.

1908 Hugh Moore, a Harvard drop-out, invents the water cooler and paper cups.

1908 Assembly line invented by Henry Ford to build his Model T.

1910 Salvarsan, a syphilis cure, is the first rationally produced medicine (with a chemical structure devised to produce a reaction).

1913 Brillo pad invented by Milton B. Loeb, a lawyer.

1913 Crossword invented by New York World newspaper.

1914 First World War introduces automatic weapons and chemical weapons.